In most forms of curtain wall constructions, the prevention of water and water vapor penetration and interior collection of moisture due to internal condensation have presented challenges for various elements of the curtain wall system.
Sealing
Sealing elements or gaskets in curtain wall constructions usually include either extruded or molded parts made from a wide variety of compounds (for example EPDM rubber, PVC, Silicone, or TPE) that require the application of an additional sealant in order to complete sealing of the curtain wall aluminum structure at the joint interfaces and in order to also provide a continuous seal between the numerous sealing elements. Up to now, EPDM foam is typically used for thermal insulation and for not for sealing.
Sealing elements are usually small and seal the perimeter of a single glazed windows to both (two sealing elements are installed per curtain wall).
In curtain wall structures, the sealing plane is typically made up of layered materials, for example the inside surface of the glass pane—gasketing material—the aluminum profile of the curtain wall structure, a pattern that repeats itself for each daylight opening in the frame. Variations in the arrangement of the components can be observed depending on the conditions in which the curtain wall is used.
Moreover, conventional curtain walls use a liquid sealant (for example butyl, silicone) to ensure sealing of aluminum parts between themselves and to ensure sealing of non-continuous gaskets between themselves and to the aluminum. Furthermore, expansion joints also require a liquid sealant to prevent any leakage.
Thermal Insulation
In typical curtain wall constructions, thermal insulation is provided by a rigid or semi-rigid barrier made of PVC (Polyvinyl chloride), polyamide, EPDM (ethylene propylene diene monomer), TPE (thermoplastic elastomer), Nylon 66 (isobar) or any other insulating material for example. EPDM foam is sometime used between two sealed elements of the wall, such as the mullion and an outside element (such as a pressure plate or rail) holding the glass pane to the mullion, but never in front and behind the elements. Furthermore the size of the thermal insulation elements is usually small and does not cover up the structural mullion, nor the glass retaining element surfaces.
Standard curtain walls can also have components screwed directly into the thermal barrier between two sealed elements.
Steel Reinforcement
Steel reinforcements in curtain walls are typically floating upon insertion in the aluminum profile of the mullion body, and are typically mechanically fastened to the mullion on a hidden face only, or on a bracket or shear block.
Water Drainage of Cavities at Each Daylight Opening
To ensure proper control of any water within the system and to apply a rainscreen principle, water collected within the system must be compartmented at each daylight opening and drained to the outside at each location. Moreover there must be a means of letting air flow from the outside to the drained cavity to ensure proper pressure equilibrium and to facilitate expulsion of any water from the cavity to the outside.
Expansion Joints
Standard curtain wall systems allow for a vertical displacement ranging from ⅛ inch to ½ inch and the movement is taken up by a gap between to vertical elements that are mechanically kept aligned and the movement is taken up by a gap between two vertical elements that are kept aligned with an internal sleeve or an external guide. The continuity of the sealing plane is usually obtained by means of an on-site applied sealant between the adjacent mullions. The discontinuity of the glass retaining element (pressure plate or rail) is also present at this location but can be staggered from the inside mullion joint. Often, expansion joints do not offer any thermal break structure. Moreover, conventional expansion joints have no system for a temporary installation locking system for ease of installation. Additionally, standard expansion joints need liquid sealants for sealing.
There is therefore a need for curtain wall elements that address at least one of the above-mentioned disadvantages associated with conventional curtain wall elements.